What is drift? Drift types

At present, the meaning of the word "drift" can be applied immediately in several fields of science. This term extends to geography, optics, anatomy, and many other areas of activity.

Drift of continents

In 1912 the German scientist Alfred Wegener proposed a heuristic theory of the infinite displacement of continental masses. The geologist made such conclusions, based on his own observations and discoveries. What is the drift of the continents? Wegener assumed that continents are in constant motion, but the speed is so small that it can not be felt. At the beginning of the 20th century such a report caused a lot of criticism and ridicule on the part of the academic world.

It is worth noting that the continental drift was discovered long before the German geologist. In the 1620s the well-known enthusiast Francis Bacon noted in his manuscript writings certain coincidences in the outline of the coast of America and Africa. On the basis of his notes, after decades, the idea of moving the continents was put forward by Frenchman Franco Plaque, and then by the German Theodore Lilienthal. In 1858, the American theologian Antonio Snyder proposed a more radical theory that after the Earth cooled, the surface could not withstand pressure and split into parts. For a long time, the continental drift has not been proven. In most of Europe and the United States, this theory is still rejected. Nevertheless, in the early 1960s Soviet scientists came to the conclusion that Wegener's judgments are reliable. In turn, the concept of fixation continued to defend the famous Russian geologists M. Usov and S. Obruchev.

The theory of continental drift

At the beginning of the 20th century, Alfred Wegener traveled around the world to understand the essence and origins of all life on the planet. On the basis of numerous data from the expeditions, the German geologist determined that all the continents have a similar structural structure. Moreover, the scientist proved the commonness of the fossil fauna and flora of the continents in the past. Parallels could also be drawn through climatic zones.

According to Wegener, a granite layer first appeared on the surface of the planet. Over time, the rock outgrowths were concentrated in a large prakontinent, called Pangea. This formation dates from 500 million years BC. It was then that a single præcaque was formed. As a result of tectonic displacements Pangea began to split into small parts. So there was a continental drift.

The movement of the continents is achieved by the centrifugal forces of the Earth's rotation. An important factor is the attraction of the Sun and the Moon. Due to this, there was a distance from Eurasia of North America, and then of Africa. The Atlantic Ocean filled the giant crevice. The consequence of the Pangea split was the mountain range of the Andes and the Cordillera.

As a result of the drift, the continents of Africa and Europe collided, forming the Alps, the Himalayas, the Carpathians and other mountain ranges. According to Wegener's hypothesis, the main points of rotation of the continents were the poles of the Earth.

Ice drift

It's no secret that the frozen masses of water move through the seas and oceans due to the internal flow. But what is the drift of ice? This is by no means a free movement on the surface of the water. In this case, it is the motion of icebergs in the ocean or sea under the influence of winds and various currents. The most ice drifts in the Arctic, where research does not stop for a day. Such movements are mainly represented by anticyclonic movement, in other words, clockwise. As a result of this cycle, the ice leaves the Arctic Ocean to the shores of Greenland in three streams. This way a small iceberg will need from 1 to 5 years depending on the initial point of the break. The trajectory of the movement depends on the Greenland current.

The first for a unique phenomenon began to observe the scientist F. Nansen back in 1893. Then the ship "Fram" drifted from the Novosibirsk coast to the Greenland Sea. Nansen tracked the relationship between the characteristics of ice throughout the entire 3-year path of the expedition. As a result, the scientist revealed two important rules: the iceberg drift velocity is approximately 2% of the speed of the accompanying wind, and the direction of motion lies 30 degrees to the right of the current. The data of Nansen was later confirmed by the Soviet professor Vladimir Vize.

Baric ice drift

This unique natural phenomenon from 1913 to 1940 in the waters of Greenland studied dozens of expeditions, and each time scientists agreed that Nansen was right in his writings and conjectures. In the late 1930s, the Soviet Union launched into the Arctic a whole network of weather stations. The project was headed by scientist N. Zubov.

According to the information received, he and his team succeeded in revealing the regularity of the drift that occurs along the isobars. As it turned out, the current in the Greenland waters is extremely weak, but very strong wind. It was he who drove the ice floes to the shores of the big islands. Thus the baric drift was discovered. He answered two rules: 1. Directions of movement of ice and isobars coincide. At the same time, the pressure is significantly increased in the right region.

2. The speed of movement is inversely proportional to the distance between the isobars.

As for the angle of 30 degrees, this deviation occurs under the influence of the Coriolis force and friction.

Gene drift: definition

In the human body at the cellular level, millions of automatic processes occur. One of the most interesting and unique of them is genetic drift. This is almost the only mechanism that is conditioned by random static phenomena. So what is gene drift? This is a chaotic change in the frequency of gene alleles, that is, variations in the population.

The mechanism of the phenomenon lies in the procedure of reproduction, which results in the formation of a huge number of gametes, called gametes. These cells are not capable of forming zygotes, but there are rare exceptions. It is from these that unique species form in the population. It should be noted that the shift in the frequency range of alleles is possible only with respect to one previous generation.

Due to drift, evolution of species occurs in local populations. It is important to understand that such a change in frequencies arises independently of any factors.

Drift of genes: population waves

This process does not in any way affect the number of species, since the ups are always followed by recessions. Many scientists are still wondering what the drift of genes is about evolution. This is what Russian scientist S. Chetverikov tried to answer in his studies. He drew attention to the regular fluctuations in the number of populations. During the experiments it was revealed that it is these processes that play a decisive role in the evolution of all life on the planet. Population fluctuations were called population waves. The genetic structure of man is constructed in such a way that at the right time to produce offspring - a new specimen of a similar species. In animals and plants, population waves depend on the territorial feature. Only species with the original genetic code can appear in a certain zone. Nevertheless, alleles are responsible for the evolution in fauna and flora.

Drift of genes: molecular evolution

The end result of the phenomenon will be the complete disappearance from the population of one allele and the securing of another in it. The higher the gene drift level, the faster the molecular evolution of the species. As studies show, the probability of fixing a moving allele is equal to the frequency of the population.

It is noteworthy that each such molecule of the gene appeared sometime as a result of a mutation. Evolutionary jumps occur at a frequency of about 10-5 per gene / gamete. It is logical to assume that the lower the population level, the lower the probability of a new mutation.

Nevertheless, many scientists believe that the degree of evolution does not depend on the number of species and the number of drifting genes. American researchers Polling and Zuckerkandl revealed that neutral alleles move at a constant rate. This applies to any species.

Electron drift

This process is a motion of charged particles under the action of a static field. Moving can be erratic and logical. Everything depends on the conductivity of the electric field. The drift of particles in gases and metals under the action of a current is determined by thermal motion. In this case, you will not be able to anticipate the speed and direction of movement. The fact is that the thermal effect does not form a single macroscopic flow of charged particles. Here the connection between electrons and the field is characterized by the intensity and density of the medium. In a plasma, the particles are under the action of a magnetic field, so the motion will be uniform and regular.

The drift velocity of charges in an electric field is much higher than that of ions. This is due to a stronger impulse of the medium.

Drift in direct current

In the amplifier Fri there is one main problem - spontaneous voltage drop. This phenomenon was called the drift of zero. As a result of switching off the current at the output of the amplifier, the value of the indicator falls to the initial value. Zero drift is most often observed in the absence of an input signal.

The reasons for this disconnect might be:

- power supply failure;
- instability of resistors or transistors;
- low-frequency noise;
- high medium temperature;
- Guidance or interference. The most rare and complex consequence of current disconnection in the UTT can be galvanic coupling between the cascades. It quickly transmits changes in signals, so instability at the input is almost not tracked.

To neutralize the drift of zero, you can use thermal compensating components, deep OOS, DC converters, a mechanism for detecting states. It would be superfluous to change the balance sheet of the UPT.

Eye drift

This process is caused by a smooth slow displacement of the eyeball. In other words, it is involuntary fixation of the central part of the retina on any object. Logically, the question arises about what is the drift of the eye and what are its causes.

To answer it you need to understand that the human retina has 3 types of movements that are not even felt: constant tremor, jerky fixation and smooth movement. The first state is the norm. The frequency of contraction of the eye muscles is up to 80 Hz. The second condition is also within the norm. The mechanism is controlled by a sudden reaction. The third state is allowed only together with the first two, but not separately. It can be caused by negation of the feedback mechanism by the retina.

Ship drift

Displacement of the vessel from the course occurs most often under the influence of strong winds. The main characteristic of this drift is the angle between the lines of the true and false directions of the route. The demolition of the vessel can occur under the influence of the current. The drift also denotes displacement in the "anchored" position, when the cargo creeps along the bottom.

The most dangerous consequence of such a demolition is the probability of the vessel landing on rocks or shoal. To exclude such a situation, it is necessary to direct the ship with its nose against the wind.